NASA's Hubble Space Telescope snapped these images of the asteroid Vesta in preparation for the Dawn spacecraft's 2011 visit to the asteroid.

Each of the four Hubble images captures views of Vesta during its 5.34-hour rotation period. Hubble's sharp "eye" can see features as small as about 40 km (25 miles) across in these images. Vesta was 211 million km (131 million miles) from Earth when Hubble made the observations.

Astronomers combined views of Vesta in near-ultraviolet and blue light to construct these images. The images show the difference in brightness and color on the asteroid's surface.

Vesta is somewhat like our moon, with ancient lava beds (the dark patches) and powdery debris, the pulverized remains of impacts (the orange-colored areas). The flattened area on one end of Vesta, visible in the top row of images, is a giant impact crater formed by a collision billions of years ago. The crater is 460 km (285 miles) across, which is close to Vesta's roughly 530-km (330-mile) diameter. Vesta is about the size of Arizona.

Astronomers used the images, taken with Hubble's Wide Field Camera 3, to better determine Vesta's spin axis. Based on the Hubble observations, astronomers calculated a slightly different, and more precise, rotation axis for Vesta.

Hubble has kept its "eye" on Vesta for more than 15 years, beginning in 1994. Hubble images of Vesta in 1997 helped astronomers discover the asteroid's immense impact crater.

Vesta is one of the largest of a reservoir of about 100,000 asteroids, the leftover material from the formation of our solar system planets 4.6 billion years ago.